Photo Gallery - Video DVD - Sound Problems

I have recent complied a video dvd of photos for the family. I chose some
music to play in the back ground. The slide time was around 1 hour and 10 (8
seconds a slide) so chose roughly the same amount of music. Yet when I
preview or burn there are gaps in the music of around 2minutes and the chosen
music never gets to the last 5 tracks.
I have tried change length to suit music, I have shuffled tracks around etc
but no joy does any one have an answer?